This invention relates to a breakaway unit for coupling a tool holder to the wrist of a robot arm.
Many procedures used in industrial processes can be performed with robots, particularly where procedures are repetitive or can be programmed for continuous operation. The present invention primarily relates to a breakaway unit for an industrial robot. However, the concepts and structure described herein can be applied to any robot having a tool holder where contact by the tool or holder can be determined to the object being worked, or to the tool or holder at the end of a robot arm. By modifying the size and construction of the unit, the breakaway coupler can be applied to robots used in science and medicine as well as robots used in specialty environments where conditions require an inanimate device to manipulate objects. Since safety couplers are a virtual necessity for powerful industrial robots, a variety of different mechanisms have been proposed for releasing the tool and tool mount at the wrist connection at the distal end of the robot arm.
In particular, the preferred embodiment of this invention is advantageously employed as a coupling device of the class referred to the industry as a breakaway, shock sensor, load limiter, collision sensor, torch mount, safety mount or other such term.
Modern industrial robots are fast, powerful and expensive. With an inertial base commonly weighing 10-40 times their own maximum payload, a payload capacity on the arm can be accelerated in excess of 2 G's. However, a robot cannot instantly stop the travel of the payload instantly during an emergency stop. Even robots having dynamic breaking may not have brakes at all axis (joints) of the robotic positioner, and significant distances may be traveled before stopping. Substantial damage or injury may result to any thing or any person in the path of travel. Most often collisions occur between the robot tool at the distal end of the arm or positioner of the robot another object. Dynamic breaking activated by contact or proximity sensors will not instantly halt travel of the tool and damage to the tool may occur if provision is not made for collision.
Among the mechanisms heretofore constructed to solve this problem are spring devices where coupler elements have a spring loaded engagement. These spring devices generally have the characteristic of increasing forces on the tool as the tool deflects and the resistance springs are compressed before release. Certain couplers have destructible elements that fail upon exceeding a design force. Generally the coupler must be removed and the element replaced before operation can continue.
Other tool mounts allow only a limited range of tool deflection before the deflection mechanism "bottoms out". This range may be insufficient for a high speed or high inertial collision, and damage to the tool or contacted object is likely.
Tool mounts that do provide for reasonable omnidirectional crash protection are complex and expensive, and in general do not provide adjustability for protection of lightweight tools.
Although magnetic couplers have been used in a breakaway tool mount, the units apparently lack a means for adjusting the magnetic coupling force and fail to provide for safe recoupling of a separated unit. Because of the strong magnetic forces required to maintain a unit in a coupled state, injury can occur when fingers interposed between magnetic components during the coupling process.